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Extract
DNA with household materials and see it with your own eyes! Materials
- Kiwi (OR 2 strawberries OR half a frozen banana)
- Table salt
- Bottled water
- Clear cup
- Spoon or straw
| - Tape or elastic band
- Liquid dish detergent
- Cheesecloth (3 layers)
- Cold isopropanol (purchase at pharmacy, place in the fridge to cool)
- Wooden or glass stir stick
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Preparation
- Make the buffer solution by mixing 1 teaspoon of
table salt in 100 mL water
- Make the soap solution by mixing 3 mL (3/4 teaspoon)
liquid soap with 27 mL (2 tablespoons) water
The
salt solution will help precipitate proteins and carbohydrates
away from the DNA
Step
1
- Scoop out the kiwi flesh into a resealable bag and
mash for 2 minutes
Mashing helps
to break apart the cells and loosen the tough cell wall
Step
2
- Add 10 mL of buffer solution and grind for at least
5 minutes. Use your weight and strength to really
mash it up!
Step
3
- Assemble the filter by covering the top of a cup
with the three layers of cheese cloth.
- Tape (or use an elastic band) the cheese cloth around
the cup.
Step
4
- Pour the kiwi mash through the filter. Let the solution
drip into the cup.
- You can get extra juice by squeezing the kiwi through
the cloth.
Step
5
- Add 3 mL of the soap solution to the filtered liquid.
- Swirl gently to mix.
The soap will
help break open the cellular and nuclear membrane to
release the DNA
Step
6
- Pour 2 volumes* of the cold isopropanol down the
length of a straw (or the back of a spoon) into the
kiwi liquid.
- The isopropanol needs to form a layer on top of
the kiwi liquid.
*Two
volumes = twice the amount of kiwi liquid Step
7
- Let the liquid sit. The DNA should precipitate where
the kiwi liquid meets the alcohol. You can use the
stir stick to spool some out of the cup!
DNA dissolves
in water but precipitates in alcohol!
The above activity is fun for all ages.
It is particularly useful in grades 9, 10, 11, and 12 to introduce various discussions about DNA.
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